In vitro insecticidal and repellent activity of Cymbopogon essential oils and geraniol against cat flea

Ctenocephalides felis felis is the most prevalent tick species infesting domestic animals and represents an important target for sustainable ectoparasite control. This in vitro study investigated the insecticidal and repellent activity of essential oils from Cymbopogon nardus, Cymbopogon winterianus, Cymbopogon flexuosus, and Cymbopogon martinii, as well as the monoterpene geraniol, against all developmental stages of cat fleas. The chemical composition of the essential oils was determined by gas chromatography with flame ionization detection. Insecticidal activity was evaluated using a contact bioassay involving filter paper impregnated with different concentrations of the essential oils and geraniol. Lethal concentrations were estimated using Probit analysis. Residual efficacy was assessed by exposing adult fleas to treated filter paper and recording mortality at 24-hour intervals, and repellency was evaluated by comparing the distribution of adult fleas between treated and control filter paper strips. All treatments showed concentration-dependent activity. Geraniol presented the lowest LC₅₀ values for eggs (14.7 μg.cm⁻²), pupae (47.1 μg.cm⁻²), adults (84.6 μg.cm⁻²), and biological cycle inhibition (3.6 μg.cm⁻²), whereas C. martinii essential oil was the most potent against larvae (LC₅₀ 19.4 μg.cm⁻²). With regard to residual adulticidal activity, C. martinii essential oil and geraniol-maintained activity for approximately 25-26 days, whereas C. nardus, C. winterianus and C. flexuosus lost activity after approximately 19-20 days. Repellency at 800 μg.cm⁻² was pronounced for all essential oils during the first hours, with C. martinii essential oil maintaining ≥ 90% repellency from 1 to 48 h, and geraniol from 1 to 12 h. These findings indicate that Cymbopogon essential oils, particularly C. martinii, and geraniol have significant in vitro insecticidal and repellent activity against C. felis felis.